Threaded self-locking device



Nov. 7, 1950 A. H. LAMB THREADED SELF-LOCKING DEVICE Filed March 17, 1945 II 1% I0 Patented Nov. 7, 1950 THREADED SELF-LOCKING DEVICE Anthony H. Lamb, Hillside, N. J., assig'nor to Weston Electrical Instrument Corporation, Newark, N. J., a corporation of New Jersey Application March 17, 1945, Serial No. 583,237

1 Claim. (o1. 1513s) This invention relates to threaded self-locking devices, and more particularly locknuts or lookscrews that afford a follow up or resilient clamping of the connected parts.

The invention is not limited in its application to a particular field or to a particular size or range of sizes but it has been especially useful in the manufacture and servicing of precision electrical instruments and instrument type relays. The types of lccknuts and lockscrews that are now manufactured commercially or that have been proposed in the past are not adapted for use in precision instruments for a number of reasons. None of the present commercial types provides the resilient clamping that is essential where plastic parts or gaskets are to be held under compression. Furthermore, none of the prior locknuts and lockscrews can be manufactured in small sizes to meet thedesign requirements for electrical instruments and relays.

Some of the nuts employed in instrument relays have an internal diameter of 10 mils, an external diameter'of 30 mils, and 200 threads to the inch. It is obviously impossible to recess a nut of this minute size to receive a fibre or spring Washer and the practice therefore has been to employ separate washers of the resilient splitring type. The lockwashers were stamped from thin sheet metal and in the smaller sizes had a thickness of about mils and an outside diameter of some 30 mils. These minute lockwashers must be separately handled in the manufacture and servicing of instruments and relays, and washers of the wrong size or shape have been used at times and quite often lockwashers have been lost in the instrument and not recovered. There are approximately thirty lockwashers in some relays and the separate handling of these washers adds materially to manufacturing costs, and may result in defective operation when lockwashers are lost within the instrument or relay.

Objects of the present invention are to provide unitary lockwasher-threaded device assemblies that eliminate the disadvantages of the prior assemblies in which separate resilient lockwashers were employed. An object is to provide selflocking threaded devices, nuts or screws, in which resilient lockwashers are brazed, soldered or welded to the threaded devices. A further object is to provide self-locking and resilient threaded devices that may be manufactured in sizes far smaller than has been possible in the past.

These and other objects and advantages of the invention will be apparent from the following specification when taken With the accom-, panying drawing in which:

Fig. 1 is a plan view of an instrument type re-. lay in which parts are resiliently clamped in place by threaded self-locking devices embodying the invention; 7

' Fig. 2 is a fragmentary perspective view of the casing and cover plate of the relay shown in F 1;

Figs. 3 to 5 areside elevations, on a greatly enlarged scale, of different forms of unitary lock washer-nut-assemblies embodying the invention;

Figs. 6 to 8 are end elevations as seen from the lockwasher ends, of the locknutsillustrated in Figs; -3 to 5, respectively.

Fig. 9 is a side elevation of a lockscrew embodying the invention; and

Fig. 10 is an end elevation of another form'of locknut in which a short locking member is used;

As shown in Figs. 1 and 2, an instrument type relay includes a coil I pivotally mounted in the gap between the ends 2, 2 of a'permanent magnet and carrying a contact arm 3 that cooperates with stationary contacts 4, 4 to close a circuit under preselected operating conditions. A considerable number of mechanical and electrical connections in such relays have been of v the screw and nut type with separate resilient or split lockwashers but, for purposes of illustration, the drawing shows only the novel threaded connections at the exterior of the casing of a small relay of the type that is described and claimed in my copending application Ser. No. 555,696, filed Sept. 25, 1944, Relay Circuits and Relays, which matured into Patent No. 2,440,861 on May 4, 1948. This relay differs from prior practice in that an inadvertent closure of the relay circuits is positively prevented by resilient blocking arms 5, 5' mounted on the transparent cover 6 of the instrument case, the blocking arms having dependent portions 1, 1' that limit the displacement of contact arm 3 to a small angle a so long as the resilient arms are tied to each other by a fusible Wire 8. The resilient arms 5, 5' are secured to the cover plate 6 by terminal screws 9 upon which nuts It, with permanently attached resilient lockwashers l I, are threaded. Terminal lugs l2 are secured to the screws 9 by similar nut-lockwasher assemblies II], II for receiving leads of the control circuit by which current is supplied to melt the fuse wire 8, thereby conditioning the relay for operation as the resilient arms spring apart to permit engagement of the relay contact arm 3 with contact A or 4 when 3 the current through the relay coil l reaches a preselected value.

The cover plate 6 is preferably a transparent plastic, and it is detachably secured to the upper flange of the metal wall I3 of the relay case to permit removal for a checking of the relay. The cover plate is resiliently compressed against the flange by screws l4 that have heads soldered or brazed to the lower face of the flange, and unitary self-locking locknut assemblies comprising nuts I0 and resilient lockwashers ll of the same type but of larger size than the nut-lockwasher assemblies l9, II that are used on the screw terminals 9.

In accordance with this invention, the nuts l0 and spring lockwashers I l are separately formed and permanently connected by welding, brazing or soldering to form a unit that facilitates the application and removal of the nuts and lockwashers, and that substantially precludes the loss of the relatively minute .lockwashers withinthe relay case. As illustrated on an enlarged scale in Figs. 3 and 6, the spring lockwasher II is secured to the nut In by a spot weld [5 at or adjacent an end of the lockwasher. The lockwasher II is so shaped as to avoid a bite on the cover plate 6 or other surface that it may engage but, as shown in Figs. 4 and 7, the lockwasher l la may be shaped to obtain a bite! ,on the engaged surface. As illustrated in Figs. 5 and 8, a radially-split and helical lockwasher I la may be secured to the nut ill by a spot eld l5a at a point substantially midway between the ends of the lockwasher. The ends of the lockwasher are overlapped in conventional manner, and both ends are spaced from the'adjacent' end surface of the nut l9. 'The bolted connections do not loosen under vibration nor as a result of bolt stretch or a shrinkage of non-metallic parts such as, for example, a relay cover plate 6 of transparent plastic material. The helical spring Washers II or Ila afford a follow up or resilient clamping action since the washers are coaxial with the nuts and are not threaded, i. e. the internal diameter of thewasher is somewhat greater than the root diameter of the threads of the associated nut.

The spring washers may be attached to screws,

for example as shown in Fig. 9, by welding or soldering the lockwasher II to the lower face of the head of the screw [6.

It-is convenient to employ the conventional lockwashers that are formed as one turn of a helix of resilient metal but, as shown in Fig. 10, a resilient locking element I? of substantially less angular extent than 360 may be secured to a nut H! by a spot weld I8.

The several illustrated embodiments are typical of the invention and it is to be understood that other variations are possible within the scope of the invention as set forth in the following claim.

I claim:

A self-locking assembly for threaded engagement with a screw; said assembly comprising a nut with a threaded bore and a flat inner end surface, and a lockwasher consisting of a one-turn helix of resilient metal-having a point substantially midway of the ends thereof welded to said flat, inner end surface of the nut, the ends of the lockwasher being overlapped and both ends being spaced from the adjacent flat end surface of the nut, thearea of a face of said lockwasher being not less than the area of said end surface of the nut and the internal diameter of the lockwasher being greater than the root diameter of the threads of the nut. Y

. ANTHONY H. LAMB.

REFERENCES CITED The following references are of record in the file of this patent: r

UNITED STATES PATENTS 

